<form action="<?php echo url_for('producto_search') ?>" method="get">
  <input type="text" class="text-busq" name="query" value="<?php echo $sf_request->getParameter('query') ?>" id="search_keywords" />
      <input class="text-busq-input" type="image" value="search" src="/images/frontend/menu/ico-buscar.png"/>
</form>